1. Field of the Invention
This invention relates to a sheet feeding apparatus and, more particularly, to an original document feeding apparatus, switchable of conveyance routes for original documents when the original documents formed with images on either one side or both sides thereof are to be read, and to an image forming apparatus using the original document feeding apparatus.
2. Description of Related Art
Automatic original document feeding apparatuses have been known so far in which an original document is automatically fed to a designated reading position to read its image information. As constitution to perform switching conveyance routes of the original document after the image thereon has been read, generally, a mechanism switching conveyance routes is pivotally arranged at a branching-off point of the routes so that the mechanism selects particularly during continuous reading of the original documents, if contacting an original document at which the image thereof is being read, the switching mechanism gives shocks to the original document, thereby causing image distortions or whatever. Hence, the reading position and the switching mechanism are designed to be isolated sufficiently, or the switching mechanism operates before the next original document is sent, thereby preventing the mechanism from contacting the original document at which the image is being read. Accordingly, its conveyance routes of original documents become longer, or longer periods of time intervals between documents increase processing time of original documents. Specially with updated digital image forming apparatuses having capabilities, such as, digital reading and memory retention, because copying becomes faster, it is difficult for the updated apparatuses, as their copying itself is done with a high speed, to complete reading of the original document within the copying time. To solve this problem, it is necessary to improve original document conveyance speed as well as to minimize the intervals between original documents. From such a view point, it is required to minimize time needed to switch the conveyance routes. However, there is a practical limit to shorten the time to operate the switching mechanism, and there is no workable way for an apparatus operating with smaller interval between original documents and higher conveyance speed.